With the increase of integration level and the improvement of element density of semiconductor integrated circuits and semiconductor devices such as multilayer wiring devices, and as wire spacing becomes narrower, wiring delays due to increased capacitance between wiring lines becomes a problem.
The wire delay T is affected by wiring resistance and capacitance between wiring lines, and is a property represented by:T∝CRwith R being wiring resistance and C being capacitance between wiring lines.
In this formula, the capacitance C between wiring lines is represented by:C=∈S/D with D representing a wire spacing, S, an electrode area (area of facing wire line surfaces), and ∈, a dielectric constant of an insulating material provided between the wiring lines.
As a result, lowering the dielectric constant of the insulating layer is an effective way to reduce the wire delay.
Conventionally, inorganic films of such as silicon dioxide (SiO2), silicon nitride (SiN) and phosphorus silicon glass (PSG) or organic polymers such as polyimide have been used as insulating materials.
However, the relative dielectric constant of a CVD-SiO2 film, which are used most commonly in semiconductor devices is about 4. In addition, even the relative dielectric constant of a SiOF film considered as a low dielectric constant film is about 3.3 to 3.5.
Under these circumstances, Nanoclustering Silica (NCS), which is a silica uniformly distributed holes with a size on a nanometer order, has been developed as a promising interlayer insulating material of low dielectric constant. The relative dielectric constant of this material is 2.25 which is drastically lower than that of conventional materials. Application of this material to an integrated circuit is considered.
However, it is known that in the case of a semiconductor device using copper wiring lines, if substances of silicon oxide series are used as interlayer insulating films, copper that is a substance of wiring diffuses in the insulating layer, deteriorates the electrical properties of the insulating layer and has a fatal impact on the device operation. As a result, a film whose one purpose is to prevent copper from diffusing is disposed between the interlayer insulating film and the wiring lines. This film may be called a diffusion prevention layer or a barrier layer.
Each of a conductive material and an insulating material can be used as a barrier layer. Which material to use is selected accordingly and arbitrarily depending on things such as which location to apply it to. When it is necessary to use an insulating material to form a barrier layer, the dielectric constant between wiring layers becomes higher by allocating this film because generally the dielectric constant of the material to form the barrier layer is higher than that of the material to form an interlayer insulating film.
As a result, when all the substances allocated between wiring lines are collectively considered, a semiconductor device that can reduce an effective “dielectric constant”, that is to say, the semiconductor device that can reduce the capacitance between wiring lines and have few problems of delaminations or cracks between the wiring layer and the barrier layer, consequently, can reduce the capacitance between wiring lines and realize a high performance of the device, is demanded.